The present invention relates to processes for making non-aqueous liquid laundry detergent compositions which contain an anhydrous anionic sulfated or sulfonated surfactant, a non-aqueous liquid surfactant, a hydrotrope, and optionally, but preferably, other conventional detergent ingredients, as well as processes for drying (removing water from) detergent ingredients, especially surfactants for use in detergent compositions, especially the non-aqueous liquid laundry detergent compositions of the present invention. In addition to the above, the present invention also provides a means for drying such detergent ingredients without the need to reclaim the solvent used in the process.
Liquid laundry detergent products offer a number of advantages over dry, powdered or particulate laundry detergent products. Liquid laundry detergent products are readily measurable, speedily dissolved in wash water, non-dusting, are capable of being easily applied in concentrated solutions or dispersions to soiled areas on garments to be laundered and usually occupy less storage space than granular products. Additionally, liquid laundry detergents may have incorporated into their formulations materials which would deteriorate in the drying operations employed in the manufacture of particulate or granular laundry detergent products. Because liquid laundry detergents are usually considered to be more convenient to use than granular laundry detergents, they have found substantial favor with consumers.
Although liquid laundry detergents have a number of advantages over granular laundry detergent products, there are also disadvantages entailed in using them. In particular, laundry detergent composition components which may be compatible with each other in granular products may tend to interact or react with each other in a liquid, and especially in an aqueous liquid environment. Components such as surfactants, perfumes, brighteners and non-aqueous solvents can be especially difficult to incorporate into liquid laundry detergent products with an acceptable degree of compositional stability. Poor compositional stability may cause the detergent composition to degenerate into an unaesthetic, ineffective, heterogeneous detergent composition during storage.
One approach for enhancing the chemical compatibility and stability of liquid laundry detergent products has been to formulate substantially anhydrous non-aqueous liquid laundry detergent compositions. Generally, the chemical stability of the components of a non-aqueous liquid laundry detergent composition increases as the amount of water in the laundry detergent composition decreases. Moreover, by minimizing the amount of water in a liquid laundry detergent composition, one can maximize the surfactant activity of the composition. Non-aqueous liquid laundry detergent compositions have been disclosed in Hepworth et al., U.S. Pat. No. 4,615,820, Issued Oct. 17, 1986; Schultz et al., U.S. Pat. No. 4,929,380, Issued May 29, 1990, Schultz et al., U.S. Pat. No. 5,008,031, Issued Apr. 16, 1991; Elder et al., EP-A-030,096, Published Jun. 10, 1981; Hall et al., WO 92/09678, Published Jun. 11, 1992; and Sanderson et al., EP-A-565,017, Published Oct. 13, 1993.
But, non-aqueous liquid laundry detergents come with their own set of disadvantages and problems. The desirable advantage of having excellent compositional stability may also mean that the non-aqueous liquid laundry detergent will have poor solubility and dispersion properties in the wash liquor inside an automatic clothes washer. Also non-aqueous liquids typically have awkward rheological properties, displaying a tendency known as xe2x80x9cshear thickeningxe2x80x9d, where the viscosity of the paste or liquid increases with an increasing shear rate, making the paste difficult to pump, store and transport. Moreover, non-aqueous liquid laundry detergent compositions are difficult and expensive to manufacture. A drying step requiring prolonged heating and stirring is necessary to eliminate the water. However it is not only difficult to consistently achieve the proper heating and stirring conditions in a manufacturing setting, but also such drying operations may have the effect of decomposing or evaporating individual components of the detergent composition. The resulting difficulty and expense involved with working with such fluids have greatly reduced their utilization as laundry detergent compositions.
The incorporation of surfactants into various consumer products, especially detergent products, such as granular detergent products and liquid detergent products, substantially anhydrous liquid detergent products in particular, is a common step in the manufacture of such products. However, the incorporation of such surfactants can present challenges to formulators, especially in the case of substantially anhydrous liquid products, because conventional surfactants, such as alkyl benzene sulfonate surfactants, are typically only available in the form of an aqueous paste prior to being processed into the products.
Given the foregoing, there is clearly a continuing need to provide processes for preparing non-aqueous liquid laundry detergent products that have a high degree of chemical and compositional stability, contain the essential components of a liquid laundry detergent composition, have a high surfactant activity and are readily soluble in a wash liquor. In addition, such processes should be easily replicated at multiple production sites and should produce liquid laundry detergent products that can be easily pumped, stored and transported.
The present invention fulfills the needs described above by providing processes for making soluble, preferably water-soluble, substantially anhydrous surfactant pastes and other detergent ingredients, products formed by such processes and compositions comprising such anhydrous surfactant pastes and/or other detergent ingredients.
The present invention encompasses a process for preparing a substantially anhydrous surfactant paste containing less than 5% water, comprising the steps of:
A) forming an aqueous surfactant mixture by blending, by weight of the mixture:
(a) from about 5% to about 85% of an anionic surfactant;
(b) from about 15% to about 95% of a liquid nonionic surfactant;
(c) from about 1% to about 40% of a hydrotrope, said hydrotrope comprising at least two polar groups separated from each other by at least 5 carbon atoms;
wherein the aqueous surfactant mixture has a water content from 5% to about 80% by weight of the aqueous surfactant mixture;
B) drying the aqueous surfactant mixture under vacuum to form said substantially anhydrous surfactant paste having a water content of less than 5%, said paste at room temperature (18-30xc2x0 C.) being in the form of a shear-thinning, non-Newtonian fluid, preferably having a yield value less than about 200 Pa, more preferably about 50 Pa-100 Pa at 30xc2x0 C.; and
C) optionally, adding an anhydrous organic liquid to the surfactant paste from step B to facilitate handling and transportation.
In a preferred process, the anionic surfactant is selected from the group consisting of alkyl benzene sulfonates, alkyl sulfates, alkyl ethoxy sulfates, and mixtures thereof. Preferably, the nonionic surfactant is selected from the group consisting of: alkoxylated (especially ethoxylated) alcohols; ethylene oxide (EO)-propylene oxide (PO) block polymers; polyhydroxy fatty acid amides; alkylpolysaccharides; and mixtures thereof.
Preferably, the weight ratio of hydrotrope; anionic surfactant is in the range of about 1:1 to about 1:100. Preferred hydrotropes are selected from the group consisting of 1,4 cyclohexane dimethanol, 1,6 hexanediol, 1,7 heptanediol, and mixtures thereof.
In one aspect, the organic liquid of step C is selected from the group consisting of: alkylene glycols; diethyl- and dipropylene glycol monobutyl ethers; glycol monobutyl ether; monoethylethers, monomethylethers, monopropylethers and monobutylethers of propoxy propanol; polyethylene glycols having a molecular weight of at least about 150; methyl acetate; methyl propionate; methyl octanoate; methyl dodecanoate; and mixtures thereof.
The invention also provides a non-aqueous liquid detergent composition, comprising a surfactant component which is a dried, substantially anhydrous surfactant paste prepared according to the foregoing manner, together with a non-aqueous solvent. Preferably, said surfactant paste comprises the hydrotrope, the nonionic surfactant and an anionic surfactant which is a member selected from the group consisting of alkyl benzene sulfonate surfactants, alkyl sulfate surfactants, alkyl ethoxy sulfate surfactants, and mixtures thereof. Most preferably, the non-aqueous solvent is butoxy propoxy propanol.